It is known to construct band-pass filters for high-frequency waves, in the UHF and VHF ranges (e.g. in the band of 50 to 1000 MHz), as cavity resonators with distributed reactances representing an antiresonant network at a predetermined operating frequency. Such a resonator generally consists of a grounded metallic shell, usually cylindrical, and a central conductor coaxial therewith. The central conductor, which may be linear or helically coiled, has an effective length of .lambda./4 where .lambda. is the wavelength at the predetermined operating frequency. One end of this conductor is grounded to the shell whereas the other, a quarter wavelength away, is ungrounded. The conductor thus constitutes an inductance terminating at a capacitance at its ungrounded end. It has also been proposed (see U.S. Pat. No. 3,538,463) to dispose two such conductors in a common shell, with their ungrounded ends confronting each other to form a capacitance flanked by two inductances.